1. Field of the Invention
The present invention relates to an image forming apparatus equipped with a plurality of paper feeding means, for instance, paper cassettes containing plural sheets of paper and a function to automatically change over a paper cassette to another one containing paper in the same size when the paper in the paper cassette is exhausted during the copying operation so as to be able to continue the copying operation and an image forming method.
2. Description of the Related Art
Image forming apparatus such as a copying machine, etc. to reproduce images based on digital data will converts an image obtained by reading an original document through an optical means into electric signals. Image data are obtained by applying various image processes to these electric signals and the image data thus obtained are accumulated in a memory or processed. Based on these image data, an image is reproduced on an image forming medium using an electrophotographic process while applying a laser beam.
In a prior art, there is an automatic paper cassette change function to automatically change over a paper cassette to another paper cassette when sheets of paper contained in the paper cassette are exhausted during the image reproduction so as to continue the copying operation. There are codes for adjusting the YES or NO of this automatic cassette change function. These adjusting codes can be set by a serviceman.
However, the YES or NO of the automatic paper cassette change function could be set only by a serviceman and was not possible by user or a menu.
Also, it was not possible to change over the automatic paper cassette change function for each paper cassette, for instance, to select only the NO of the automatic cassette change from the manual paper feeding. In particular, for the manual paper feeding by setting plural sheets of paper on a manual paper feed guide, special paper such as thick paper, color paper, etc. are often used. Accordingly, if paper is exhausted during the copying, the automatic paper cassette change function works and the cassette is changed over to another paper cassette provided in the main body of a copying machine, the copying continues on a different kind paper and an image will not be copied on a desired paper.
As described above, in the automatic cassette change function to continue the copying by automatically changing the cassette to another paper cassette containing the same size paper when the paper set in a manual paper feed guide or in the cassette currently feeding paper is exhausted during the copying operation, the YES or NO of this automatic cassette change function was effected only by setting adjusting codes by a serviceman. Accordingly, user was not able to set the YES or NO of the automatic cassette change function for each paper feed cassette and further, this function also could not be set by user or a menu. For instance, in the manual paper feeding, such special paper as thick paper and colored paper are often used and if paper is exhausted during the copying, the automatic cassette change function is actuated and a paper cassette is changed and different kind of paper is copied. In other words, the automatic cassette change function cannot be used effectively, for instance, the copying is made on other kinds of paper that are not desired.